Objective c UIPickerView未申报？

我遇到了一个小问题，我在下面代码的第1行遇到了一个错误，说“'UIPickerView'未声明。我从我的书中抄了出来，我不确定出了什么问题？ 我能得到一些帮助吗？非常感谢，谢谢：）

这是整个.m文件代码

#import "InstatwitViewController.h"

@implementation InstatwitViewController

- (void)viewDidLoad {

[super viewDidLoad];

activities = [[NSArray alloc] initWithObjects:@"sleeping",
@"eating", @"working", @"thinking", @"crying", @"begging",
@"leaving", @"shopping", @"hello worlding", nil];

feelings = [[NSArray alloc] initWithObjects:@"awesome",
@"sad", @"happy", @"ambivalent", @"nauseous", @"psyched",
@"confused", @"hopeful", @"anxious", nil];
}


- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)
pickerView {
return 2;
}
- (NSInteger)PickerView:(UIPickerView *)pickerViewnumberOfRowsInComponent :      (NSInteger)component {
if (component == 0) {
    return [activities count];

}
else {
    return [feelings count];
}
}


- (void)didReceiveMemoryWarning {

[super didReceiveMemoryWarning];

- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    switch (component) {
        case 0:

            return [activities objectAtIndex:row];

        case 1:
            return [feelings objectAtIndex:row];

    }
    return nil;

}
}

- (void)dealloc {
[activities release];
[feelings release];
[super dealloc];
}

@end

你把它复制到哪里了？它应该在你正在实现的类的

.m

文件的

@implementation

..

@end

部分。它应该而不是在

@接口

..

@end

部分，通常在

.h

文件中，或者其他地方，即

@imple之外校正

…

@end

部分

请显示更多的代码

编辑 这：

在

-（NSString*）pickerView:…

之前缺少结束符

}

。换句话说，将其更改为：

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

}

- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

}

- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {